Heavy Seat Knife Plate Hanger

ABSTRACT

A connection between a first, supporting structural member, such as a header, and a second, supported structural member such as a beam is provided, wherein the connection is made with a connector and fastenings, the use of which can be substantially hidden from view. The connector is designed to be inserted in a slotted opening in the second, structural member and to attach to a surface of the first, supporting structural member.

BACKGROUND OF THE INVENTION

The present invention relates to a connection between a first, supporting structural member, such as a post or header, and a second, supported structural member such as a beam or joist. The connection is typically made with a connector and fasteners, the use of which can be substantially hidden from view. The connector is inserted into one or more openings formed in the second, structural member and attaches to a surface of the first, supporting structural member. The connector is formed with a central flange, typically called a knife plate, that is inserted into the supported structural member.

German Utility Model No. 90 01 067 teaches a concealed joining element with a central flange that is inserted in the supported member that is made from a sheet of relatively thin material whose effective thickness is increased by providing deformations or beads in the sheet metal so that the knife plate of the connector will fit more snugly in the slotted opening of the supported structural member and thus prevent looseness in the connection.

German Utility Model No. 92 05 490 also teaches a concealed joining element made from a sheet of relatively thin material, but instead of providing the attachment web with deformations and beads to increase its effective thickness, the invention crimps or folds the material of the openings over themselves to increase the effective thickness of the knife plate of the connector.

German Patent No. DE 41 24 553, published in March of 1992, teaches a two-part, concealed joining element. Two similarly-shaped, L-shaped members are joined together so that their larger flanges overlap to form a knife plate that is inserted into the slotted opening of the supported structural member. The smaller flanges of the L-shaped members make up the fastening flanges that attached to the supporting structural member. The flanges that make up the knife plate are provided with deformations or embossed portions to increase the effective thickness of the combined knife plate.

U.S. Pat. No. 5,062,733, granted in 1991, teaches a concealed joining element with slots formed in the upper portion of the knife plate for receiving dowels that connect the knife plate of the joining element to the second structural member.

U.S. Pat. No. 5,598,680, granted in 1997, teaches a concealed joining element with a knife plate and fastening flanges that are bent from the knife plate to attach the joining element to the supporting structural member. An upper fastening flange extends above the top of the knife plate and a lower fastening flange extends below the bottom of the knife plate. Each fastening flange extends to both opposed sides of the knife plate.

U.S. Pat. No. 5,061,111, granted in 1991, teaches a concealed joining element with a knife plate and a fastening flange attached to the end of the knife plate. A seat plate is also attached to the knife plate and the supported member bears upon the seat plate.

U.S. Pat. No. 4,398,841, granted in 1983, teaches a concealed joining element with a knife plate and a seat plate attached to the lower bracketing edge of the knife plate. The knife plate of U.S. Pat. No. 4,398,841 is formed with hooked members at the rear edge of the knife plate that fit into slots in a block member that is part of a post.

The present invention provides a concealed joining element with a knife plate inserted into the supported structural member and a seat plate upon which the supported member rests that is economical to produce, amenable to present construction methods and achieves high load values.

SUMMARY OF THE INVENTION

The present invention provides a connection between a supporting structural member and a supported structural member made with a connector and one or more first fastenings and one or more second fastenings. The connector is constructed in such a manner that the connector has a knife plate that is inserted into a slotted or narrow opening in the second structural member and a seat plate upon which the supported structural member bears. The connector and fasteners can be substantially hidden from view.

The connector has a substantially planar knife plate. In the preferred embodiment, the substantially planar knife plate is inserted into a slotted opening in the second, supported structural member. Generally, the slot is provided at the end of the second, supported structural member. The connector is attached to the first structural member through one or more fastening flanges. The one or more fastening flanges preferably receive fasteners that are driven through the fastening flanges and into the first structural member. Some of the fastener enter into the first structural member orthogonally to the one or more fastening flanges, and some of the fastening flanges enter the first structural member at acute angles to the one or more fastening flanges. Preferably the fasteners are driven through the one or more fastening flanges in an upward direction at an acute angle to the one or more fastening flanges. Preferably the orthogonally oriented fasteners are arranged along the height of the connector so as to be interspersed with the acutely angled fasteners.

Preferably the fasteners that attach the one or more fastening flanges to the first structural member are self-drilling screws when the first structural member is made from wood or a similar material.

The one or more fastening flanges of the connector are formed with slotted openings to guide the fasteners driven at an acute angle to the one or more fastening flanges. The one or more slotted openings are also set at an acute angle to the substantially planar knife plate with the upper portions of the slotted openings directed inwardly to the knife plate with respect to the lower portions of the slotted openings such that the pin-type fasteners are inserted upwardly into the first structural member and directed towards a plane that would be an extension of the knife plate into the first structural member, depending on which side of the knife plate the slotted opening is located.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a connector used in the present invention with the fasteners used to make the connection also shown, and the second member is shown in dotted lines.

FIG. 2 is a front view of the connector of the present invention.

FIG. 3 . is a front view of an alternate connector of the present invention, similar to the connector shown in FIG. 2 .

FIG. 4 is a front view of another alternate connector of the present invention, similar to the connector shown in FIG. 2 .

FIG. 5 is a perspective view of a second structural member formed with a slot for receiving the knife plate of the connector and a connector attached to the first structural member.

FIG. 6 is a left side view of the connector shown in FIG. 1 .

FIG. 7 is a side view of a connection made according to the present invention.

FIG. 8 is a cross-sectional side view taken along line 8-8 of FIG. 9 of a slotted opening in the connector.

FIG. 9 is an enlarged front view taken along line 9-9 of FIG. 3 of a slotted opening.

FIG. 10 is a perspective view of an alternate embodiment of the connector of the present invention.

FIG. 11 is front view of the connector shown in FIG. 10 .

FIG. 12 is a back view of the connector shown in FIG. 10 .

FIG. 13 is a right side view of the connector shown in FIG. 10 .

FIG. 14 is a left side view of the connector shown in FIG. 10 .

FIG. 15 is a top view of the connector shown in FIG. 10 .

FIG. 16 is a bottom view of the connector shown in FIG. 10 .

FIG. 17 is a perspective view of the second structural member, the connector and the first structural member ready to be connected. The connector is shown connected to the first structural member.

FIG. 18 is a side view of the connection made with the members shown in FIG. 17 .

FIG. 19 is a perspective of another embodiment of the connector of the present invention.

FIG. 20 is a front view of the connector of FIG. 19 .

FIG. 21 is a back view of the connector of FIG. 19 .

FIG. 22 is a right side view of the connector of FIG. 19 .

FIG. 23 is a left side view of the connector of FIG. 19 .

FIG. 24 is a top view of the connector of FIG. 19 .

FIG. 25 is bottom view of the connector of FIG. 19 .

FIG. 26 is a perspective view of another embodiment of the connector of the present invention.

FIG. 27 is front view of the connector of FIG. 26 .

FIG. 28 is a back view of the connector of FIG. 26 .

FIG. 29 is right side view of the connector of FIG. 26 .

FIG. 30 is left side view of the connector of FIG. 26 .

FIG. 31 is a top view of the connector of FIG. 26 .

FIG. 32 is a bottom view of the connector of FIG. 26 .

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a connection 1 between a supporting, first structural member 2 and a supported, second structural member 3 made with a connector 4 and one or more first fasteners 5 and one or more second fasteners 6. Note that in some embodiments, the first structural member 2 could be the supported member and the second structural member 3 could be the supporting member. The connection 1 and the connector 4 are constructed in such a manner that the connector 4 and fasteners 5 and 6 can be substantially hidden from view. The first structural member 2 is preferably a post or a header with a generally planar attachment surface 7. The second structural member 3 is preferably an elongated joist or a beam abutting or substantially abutting the first structural member 2 at the attachment surface 7. The elongated second structural member 3 extends away from the first structural member 2, typically at an orthogonal angle.

The second structural member 3 is formed with a top surface 8, a bottom surface 9 that lies parallel to the top surface 8, and a pair of parallel side surfaces 10, all of which intersect with the abutment surface 11.

The connector 4 has a substantially planar knife plate 12. In the preferred embodiment, the knife plate 12 is inserted into a slotted opening 13 in the second, supported structural member 3. The connector 4 also has a seat plate 14. In some installations, the end portion of the bottom surface 9 of the second structural member 3 will bear upon the seat plate 14. In other embodiments, as shown in FIG. 7 , the end of the second structural member 3 will be formed with a notch 15 having a bearing surface 16 that rests upon the seat plate 14. After installation, the notch can be filled with an intumescent material or a block of material similar to the second structural member 2 to hide the connector 4 and to help protect the connection 1 from fire. Generally, the slotted opening 13 is provided at the end of an elongated second, supported structural member 3. The slotted opening 13 has two generally parallel side walls 17 that are joined by a generally straight front face 18.

The connector 4 is attached to the first structural member 2 by means of one or more fastening flanges 19. In the embodiment shown in the drawings, one fastening flange 19 is provided that extends to either side of the knife plate 12. The one or more fastening flanges 19 are connected to the rear edge 20 of the knife plate 12. In the embodiment shown in the drawings, the fastening flange 19 is substantially planar member, disposed orthogonally to the knife plate 12, but the fastening flange could be disposed at a variety of different angles for making skewed connections. The fastening flange 19 preferably receives the first fasteners 5 that are driven through the fastening flanges 13 and into the first structural member 2. Preferably the first fasteners 5 that attach the fastening flange 19 to the first structural member 2 are self-drilling and self-tapping threaded fasteners or screws when the first structural member 2 is made from wood or a similar material. As shown in FIG. 4 , preferably, openings 21 and 26 are provided in the fastening flange 19 to make insertion of the first fasteners 5 easier and to direct the user as to the placement and number of first fasteners 5 to be used. Openings 21 are preferably round openings as shown in FIG. 2 and are meant to receive a first fasteners 5 orthogonally to the fastening flange 19, and openings 26 are slotted openings meant to receive first fasteners 5 at an acute angle to the fastening flange 19.

As shown in FIG. 5 , the knife plate 12 is defined by an outer point 23 and an oppositely disposed rear edge 20 near the abutment surface 11 of the second structural member 3 and upper and lower bracketing edges 24 and 25. The outer extent of the attachment web 12 from the attachment surface 7 of the first structural member 2 is defined by the outer point 23. The inner extent of the attachment web 12 is defined by the rear edge 20 of the attachment web 12. An upper bracketing edge 24 extends from the rear edge 20 to the outermost point at the top of the attachment web 12. A lower bracketing edge 25 extends from the rear edge 20 to the outer point 23 at the bottom of the attachment web 12.

To better hide the connector 4, the end of the second structural member 3 can be routed to create a cavity that receives the one or more fastening flanges 19 and the heads of the first fasteners 5 attaching the connector 4 to the first structural member 2. Alternatively, the first structural member 2 can be routed to create a cavity in which the fastening flanges 19 and the heads of the first fasteners 5 are inserted.

The elongated slotted opening 14 in the second structural member can be a blind slot, where the slotted opening 14 in the end or abutment surface 11 of the second structural member 3 does not communicate with any other end or sides faces 10 of the second structural member 3.

As shown in FIG. 1 , the strength of the connection can be improved by driving strengthening fasteners 27 upward into the surface of the second, structural member 3 that rests on the seat plate 14 of the connector 4. As shown in FIG. 1 , the fasteners 27 have been driven through the bottom surface 9 of the second member. Multiple fasteners can be driven into second structural member 2, and are driven orthogonally to the bottom surface 8 with more fasteners used to increase the loading with 4 fasteners 27 being preferred achieving high load values.

As shown FIG. 2 , the connector 4 has a longitudinal axis 28 and a lateral axis 29, and the round fastener openings 21 and the slotted fastener openings 26 are interspersed along the longitudinal axis 28 such that a slotted fastener opening 26 may have round fastener openings 21 disposed both above and below the slotted fastener opening 26. As shown in FIG. 1 , some of the fasteners 5 inserted through the slotted openings 26 will reach up to areas where fasteners 5 are inserted through round fastener openings 21 orthogonally to the fastening flange 19 such that the fasteners 5 overlap in areas of the first structural member 2.

As shown in FIG. 9 , the slotted openings 26 are formed by making two straight and parallel cuts or slots in the material of the fastening flange 19, creating side walls 30. Side walls 30 are preferably straight. The side walls 30 or cuts are preferably of equal length and each has a first end 31 and second end 32. At the first end of the side walls 30, the side walls are not joined together and the material of the fastening flange 19 (or of the connector 4 if formed in a different part of the connector 4) is disposed between the side walls 30. At the second end 32 of the side walls 30, each of the side walls 30 intersects with a curved cut, forming relief walls 33 in the material of the fastening flange 19. The relief walls 33 are preferably curved. Each curved relief wall 33 has a first end 34 and a second end 35. The first end 34 of each curved relief wall 33 intersects with the second end 32 of the side walls 30. Each curved relief wall 33 curves away from the other opposed curved relief wall 33 and then curves back toward the other opposed curved relief wall 33. The second end 35 of each curved relief wall 33 intersects with an end cut, forming an end wall 36, that is preferably straight, that connects the two curved relief walls 33. As formed, the slotted openings 26 are preferably T-shaped with a first extended opening 391 disposed between the side walls 30 intersecting with a second flared opening 392 disposed between the curved relief walls 33 with the flared opening 392 being disposed generally orthogonally to the extended opening 391. Each curved relief wall 33 is preferably a semi-circular arc with a radius of 0.105 inches when the fastening flange material is 0.235″ thick and the width of the slotted fastener opening 26 between the farthest reaches of the curved relief walls 33 is preferably 0.60 inches.

Along each straight side wall 30, at a point between the first and second ends 31 and 32 of each straight side wall 30, a bracketing cut is made in the material of the fastening flange 19 that intersects with each straight cut 30 to form a tab end 37. This bracketing cut creating a tab end 37 defines the end of the tab 38 of the material of the fastening flange 19 disposed between the two straight side walls 30.

The tab 38 of the material of the fastening flange 19 is bent upward from the generally planar fastening flange 19 to create a guide for the angled fasteners 5. When used with fasteners 5 have a shank diameter of between 0.22 inches and 0.27 inches, the side walls 30 are preferably 1.2 inches long. The bracketing cut forming tab end 37 is made 0.36 inches from the second ends 32 of the straight side walls, and the bracketing cut is preferably made orthogonally to the side walls 30. The tab 38 between the side walls is preferably bent a little past the first ends 31 of the side walls 30. The tab 38 when it is bent upwardly has an underside that makes a 45 degree angle with the substantially planar fastening flange 19. The tab 38 projects upwardly from the substantially planar fastening flange 19 and directs the fastener to be driven at an acute angle to the fastening flange 19.

The fasteners 5 are preferably formed with flaring heads 39 and the underside of the flaring head 39 can abut against the tab end 37 when the fastener is driven into the first structural member 2.

As shown in FIG. 1 , the uppermost fasteners 5 received in the first structural member are disposed orthogonally to the fastening flange 19 and are longer than the other fasteners 5 received in the first structural member 2.

As shown in FIG. 6 , the seat plate 14 is formed with fastener openings 40 to receive the fasteners 6. The fastener openings 40 in the seat plate 14 are spaced far away from the fastening flange 19 and near the outer front edge of the seat plate 14.

The knife plate 12 preferably extends the length of the fastening flange 19 to the top of the fastening flange 19.

As shown in FIG. 7 , the connector 4 is attached to the first structural member 2 through one or more fastening flanges 19. The one or more fastening flanges 19 preferably receive fasteners 5 that are driven through the fastening flanges 19 and into the first structural member 2. Some of the first fasteners 5 enter into the first structural member 2 orthogonally to the one or more fastening flanges 19 , and some of the first fasteners 5 enter the first structural member 2 at acute angles to the one or more fastening flanges 19. Preferably the first fasteners 45 are driven through the one or more fastening flanges 19 in an upward direction at an acute angle to the one or more fastening flanges 19. Preferably the orthogonally oriented first fasteners 5 are arranged along the height or longitudinal axis 28 of the connector 4 so as to be interspersed with the acutely angled first fasteners 5.

As shown in FIGS. 6, 7, 8 and 11 , the knife plate 12, the fastening flange 19 and the seat plate 14 can be formed in a manner to create areas of mechanical interlock between the members. As best shown in FIG. 8 , the rear edge 20 of the knife plate 12 can be formed with one or more projections 41 (two are shown in FIG. 8 ) that fit into openings 42 of a corresponding shape in the fastening flange 19. The projections 41 shown in FIG. 8 are rectangular in shaped. Preferably, the projections 41 are closely received by the openings 42, and preferably do not extend past the back surface 43 of the fastening flange 19.

As shown in FIGS. 8 and 11 , the bottom edge 44 of the fastening flange 19 can be formed with one or more projections 45 (one projection is shown in FIG. 8 ) that fits in a corresponding notch 46 at the rear end 47 of the seat plate 14.

As shown in FIGS. 6 and 9 , preferably the knife plate 12 is formed with an elongated slot 48 that runs parallel to the rear edge 20 of the knife plate. The elongated slot 48 has an entrance opening 49 at the upper bracketing edge 24 of the knife plate 12. The elongated slot 48 receives dowel 50—a second fastener 6—for making a mechanical connection between the second structural member 3 and the connector 4. As shown in FIG. 12 , the second structural member 3 is formed with an opening 51 and a bore 52 in one or more of the side surfaces 10 of the second structural member that receive the dowel 50 and hold the dowel 50 in place with respect to the second structural member 3. As shown in FIG. 13 , preferably the dowel 50 is received in the elongated slot 48 at a point above the bottom 53 of the elongated slot 48.

The one or more fastening flanges 19 of the connector 4 are formed with slotted openings 26 to guide the first fasteners 5 driven at an acute angle to the one or more fastening flanges 19. The one or more slotted openings 26 are also preferably set at an acute angle to the substantially planar knife plate 12 or the center line 54 with the upper portions of the slotted openings 26 directed inwardly to the knife plate 12 with respect to the lower portions of the slotted openings 26 such that the pin-type first fasteners 5 that are inserted upwardly into the first structural member 2 are also directed towards a plane that would be an extension of the knife plate 12 into the first structural member 2, depending on which side of the knife plate 12 the slotted opening 26 is located. Preferably, the first fasteners 5 have tips 55 that enter the first structural member 2 first and a shank 56 a portion of which enters the first structural member 2 and ends 57 that do not enter the first structural member 2 but bear against the one or more fastening flanges 19. Preferably, the first fasteners 5 driven upwardly into the first structural member 2 are disposed so that the tips 55 of these fasteners 5 are disposed above the ends 57 of these fasteners 5, and the tips 55 of these fasteners 5 are disposed closer to the center line 54 of the connector than the ends 57 of these fasteners.

In one embodiment, the fastening flange 19 and the knife plate 12 are preferably made from 3 gauge steel that is approximately 0.235″ to 0.240″ thick. The fasteners 5 and 6 are preferably Simpson Strong-Tie SDCF22614 or 27614 screws with shank diameters of either 0.22 inches or 0.27 inches, and the fasteners 5 that enter the first structural member 2 orthogonally are approximately 6″ long with the longer fasteners 5 that attach the top of the connector being approximately 10 inches long. The uppermost fasteners 5 that attach the one or more fastening flanges 19 to the first structural member 2 are disposed orthogonally to the one or more fastening flanges 19. The lowermost fasteners 5 that attach the fastening flange 19 are preferably inserted 2.250 inches above the seat plate 14 and are disposed orthogonally the one or more fastening flanges 19, and the second lowest fasteners 5 are preferably inserted 3.5″ above the seat plate 14, and are disposed orthogonally the one or more fastening flanges 19. The seat plate 14 is preferably 7.750 inches long and 5.750 inches wide. The fastening flange is preferably 14″ tall, 16.5″ tall or 19″ tall, and the connectors can achieve bearing loads of 20,000 pounds, 27,000 pounds or 35,000 pounds. In the 14″ tall embodiment, preferably 8 angled fasteners 5 and 12 orthogonal fasteners 5 are used to connect the fastening flange 19 to the first structural member. In the 16.5″ tall embodiment, preferably 12 angled fasteners 5 and 12 orthogonal fasteners 5 are used to connect the fastening flange 19 to the first structural member. In the 19″ tall embodiment, preferably 16 angled fasteners 5 and 12 orthogonal fasteners 5 are used to connect the fastening flange 19 to the first structural member. As shown in FIG. 6 , the seat plate 14, knife plate 12 and fastening flange 19 are secured together preferably by welding and the mechanical interlock of the projections 41 and 45 with the openings 42 in the fastening flange and the notch 46 in the seat plate 14 respectively. 

We claim:
 1. A connection between a first structural member and a second structural member made with a connector, the connection comprising: a. the first structural member having an attachment surface; b. the second structural member having an abutment surface disposed in close proximity to the attachment surface of the first structural member, the second structural member having a slotted opening in the abutment surface; c. the connector having a generally planar knife plate inserted in the slotted opening of the second structural member, the connector having one or more generally planar fastening flanges connected to the rear edge of the knife plate, the one or more fastening flanges being disposed generally parallel to the attachment surface of the first structural member and at an angle to the knife plate, the one or more fastening flanges being attached to the first structural member by one or more first fastenings, the knife plate being attached to the second structural member by the one or more second fastenings; wherein d. the first fastenings are a plurality of elongated first fasteners, and at least one of the first fasteners is inserted upwardly and at an acute angle to the one or more fastening flanges and into the first structural member.
 2. The connection of claim 1, wherein: the connector has a seat plate attached to the knife plate, and the second structural member bears upon the seat plate.
 3. The connection of claim 2, wherein: strengthening fasteners are inserted upward into a surface of the second structural member that rests on the seat plate of the connector.
 4. The connection of claim 2, wherein: the bottom edge of the fastening flange is formed with one or more projections that are received by one or more notches in the seat plate.
 5. The connection of claim 1, wherein: the knife plate is formed with one or more projections that fit into openings in the one or more fastening flanges.
 6. The connection of claim 1, wherein: the first fasteners are self-drilling and self-tapping threaded fasteners.
 7. The connection of claim 1, wherein: a. the connector has a center line which divides the connector laterally and is parallel to a longitudinal axis of the connector and which is parallel with the knife plate of the connector, b. the first fasteners have tips that enter the first structural member first, shank portions which enter the first structural member following the tips and ends that do not enter the first structural member, the ends bearing against the one or more fastening flanges; and c. the at least one of the first fasteners inserted upwardly and at an acute angle to the one or more fastening flanges is disposed so that the tip is disposed above the end, and the tip is disposed closer to the center line of the connector than the end.
 8. The connection of claim 1, wherein: a. the connector has a longitudinal axis aligned with the knife plate of the connector; b. at least two of the first fasteners are inserted at an orthogonal angle to the one or more fastening flanges and into the first structural member; and c. the at least one of the first fasteners inserted upwardly and at an acute angle to the one or more fastening flanges is disposed between the at least two of the first fasteners inserted at an orthogonal angle to the one or more fastening flanges along the longitudinal axis.
 9. The connection of claim 1, wherein: the one or more fastening flanges are formed with one or more slotted openings, and the at least one first fastener inserted upwardly and at an acute angle to the one or more fastening flanges is received by one of the one or more slotted openings in the one or more fastening flanges.
 10. A connection between a structural member and a connector and one or more first fasteners, the connection comprising: a. the structural member having an attachment surface; b. the connector having one or more fastening flanges being disposed generally parallel to the attachment surface of the structural member and in interfacing engagement with the attachment surface, the one or more fastening flanges being attached to the structural member by the one or more first fasteners; wherein c. the one or more first fasteners are elongated fasteners, and d. the one or more fastening flanges are formed with one or more slotted openings.
 11. The connection of claim 10, wherein: the one or more slotted openings are T-shaped.
 12. The connection of claim 10, wherein: a. the one or more slotted openings are formed with a first extended opening disposed between opposed and spaced apart side walls with the first extending openings intersecting with a second flared opening disposed between opposed and spaced apart relief walls; and b. the spacing between the opposed relief walls is greater than the spacing between the opposed side walls.
 13. The connection of claim 12, wherein: the flared opening is disposed generally orthogonally to the extended opening.
 14. The connection of claim 12, wherein: the first extending openings are longer than the flared openigns.
 15. The connection of claim 12, wherein: a tab is disposed between portions of the side walls.
 16. The connection of claim 12, wherein: the side walls are substantially straight and the side walls are of substantially equal length.
 17. The connection of claim 15, wherein: each side wall has a first end and second end, and the second ends of the side walls intersects with a relief wall.
 18. The connection of claim 17, wherein: the relief walls are preferably curved.
 19. The connection of claim 18, wherein: a. the relief walls each has a first end and a second end, and b. each curved relief wall curves away from the other opposed relief wall and then curves back toward the other opposed relief wall.
 20. The connection of claim 19, wherein: the second end of each curved relief wall intersects with an end wall that connects the two curved relief walls. 